1. Field
The present invention relates to predistortion of a waveform, and more particularly, to a method and apparatus for predistorting a waveform for input to an amplifier.
2. Background
Power amplifiers typically do not behave in a linear manner. More particularly, power amplifier distortion may compress or may expand the output signal swing of the amplifier. Signal detectors receiving and decoding the amplified signals typically do not operate in such a non-linear fashion. Therefore, it is typically necessary to linearize the output of the amplifier.
One approach to such linearization is digital predistortion. Digital predistorters may be used with power amplifiers to invert the power amplifier distortion characteristics by expanding the compression regions and compressing the expansion regions in the power amplifier characteristics curve. For example, when a power amplifier compresses a waveform, the power amplifier typically compresses the peaks of the waveform. In such a case, digital predistortion may compensate for the compression by performing crest enhancement.
Digital predistortion algorithms may require time to adapt to a given amplifier. As such, it is desired to improve the efficiency of digital predistortion algorithms so as to reduce the amount of time needed to adapt to the amplifier.